This application is based on an application No. 2001-089489 filed in Japan, the content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a bulb-type lamp having a globe, such as a bulb-type fluorescent lamp and an electrodeless discharge lamp, and a manufacturing method for the bulb-type lamp.
2. Related Art
A bulb-type lamp is a kind of lamp in which a spherical globe, like the one used in an incandescent lamp, is fixed to a case. Examples of such a bulb-type lamp include bulb-type fluorescent lamps and electrodeless discharge lamps. The globe is usually made of glass in consideration of the heat generated in the lamp. Also, the globe is fixed to the case using an adhesive made of a thermosetting resin, such as a silicon resin, which has excellent heat resistance and sealing ability.
The following explains a construction of a bulb-type lamp and a method of fixing a globe to a case, taking a bulb-type fluorescent lamp as an example.
FIG. 10 is a partial broken front view of a conventional bulb-type fluorescent lamp.
This bulb-type fluorescent lamp has a globe 900, a case 910, an arc tube 920, and a holder 930. The globe 900 is made of glass and has one end opened. The case 910 is made of a resin and is engaged with the open end of the globe 900. The arc tube 920 is made up of three U-shaped fluorescent tubes which are bridge-connected. The holder 930 is made of a resin, and is housed in an envelope formed by the globe 900 and case 910. The holder 930 holds the arc tube 920 on one surface and an electric ballast 931 for illuminating the arc tube 920 on the other surface, and is fixed into an opening of the case 910.
Here, a groove 940 is formed between the case 910 and the holder 930, along the periphery of the case 910. An edge part 900a of the globe 900 is inserted in this groove 940 and bonded to the case 910 through a thermosetting adhesive 941.
Such a bulb-type fluorescent lamp can be manufactured as follows. First, the arc tube 920 and the electric ballast 931 are attached to the holder 930. The holder 930 is then inserted into the case 910 with the electric ballast 931 being inserted first. Hence the electric ballast 931 is housed in the case 910. Following this, the thermosetting adhesive 941 is injected into the groove 940 formed between the case 910 and the holder 930, and the edge part 900a of the globe 900 is inserted into the groove 940. The construction is then placed in a heating furnace and heated therein, to cure the thermosetting adhesive 941. As a result, the globe 900 is fixed to the case 910 through the adhesive 941.
With this manufacturing method, however, the globe 900 may be fixed to the case 910 in a tilted position. This causes a failure of holding the globe 900 in a correct position.
Prior to the heating process in the heating furnace, the globe 900 and the case 910 are substantially in tight contact with each other through the adhesive 941 and so the envelope formed by the globe 900 and case 910 is hermetically sealed. When the bulb-type fluorescent lamp in this state is heated in the heating furnace, the air in the envelope expands and the internal pressure increases. This being so, if the adhesive 941 is not hardened yet but is still soft, the internal pressure of the envelope may cause the globe 900 to be pushed up or tilted. If the adhesive 941 hardens in such a state, the globe 900 will end up being fixed to the case 910 in a tilted position (in more detail, the edge part 900a of the globe 900 is tilted upward on one side by about 4 mm). As a result, the globe 900 cannot be held in a correct position.
Bulb-type fluorescent lamps with tilted globes are all abandoned without being reused, because of their defective external appearances. Since these products are almost in finished form, they are costly and so abandoning them inevitably increases manufacturing costs.
To avoid the tilting of the globe, the following method may be employed instead of using a thermosetting resin as above. Which is to say, a stopper is provided to the edge part of the globe, whereas a stopper holding part is provided to the case. By engaging the stopper with the stopper holding part, the globe can be secured to the case. However, because the globe is made of glass, the stopper of the globe is not only difficult to form but also likely to break when engaged with the stopper holding part. For this reason, this type of bulb-type fluorescent lamp is not very practical.
The same problem can be found in electrodeless discharge lamps that have a construction similar to bulb-type fluorescent lamps, namely, a construction in which a globe is fixed to a case.
The present invention has an object of providing a bulb-type lamp that holds a globe in a correct position and so delivers an improved external appearance, and a manufacturing method for the bulb-type lamp.
The stated object can be achieved by a bulb-type lamp including: a globe having a constricted neck part at one end; a connector having a ring-shaped groove in which the neck part of the globe can be inserted, wherein the globe is bonded to the connector in a state where the neck part is inserted in the groove; a holder having a stand that supports an electric ballast; and a case having an opening, and holding the holder in a state where the holder is inserted in the case through the opening with the electric ballast being inserted first, wherein in the opening of the case, the connector to which the globe is bonded is fixed to one of the case and the holder by a fitting construction.
With this construction, the globe is held in place just by engaging the connector, to which the globe is bonded, with the case or the holder. This eliminates the need for the heating process which is conventionally performed after the envelope is formed by the globe and case. Accordingly, the tilting of the globe caused by the expansion of air in the envelope is prevented, with it being possible to hold the globe without a tilt relative to the case. As a result, the external appearance of the bulb-type lamp improves. This reduces the number of defective products, so that increases of manufacturing costs caused by abandoning defective products can be suppressed.
Here, the globe may be bonded to the connector in a state where the neck part which is inserted in the groove is kept from contact with a bottom of the groove.
With this construction, the tilting of the globe can be prevented more efficiently.
Here, the fitting construction may include a depression and a projection that fit together, the depression and the projection each being provided at a different one out of (a) the connector and (b) one of the case and the holder.
Here, the bulb-type lamp may be a bulb-type fluorescent lamp in which a fluorescent tube is supported by the stand of the holder, wherein the globe is a hollow spherical member having an open end at which the neck part is formed, a light diffusion film is formed on an internal surface of the globe using an adhesive, and the adhesive used for forming the light diffusion film is also used for bonding the globe to the connector.
With this construction, it becomes unnecessary to prepare another adhesive to bond the globe to the connector, since a single adhesive serves to form the light diffusion film and also to bond the globe to the connector. This contributes to lower manufacturing costs.
Here, the connector may be a ring having an inner wall and an outer wall which together form a U-shaped cross section, with the ring-shaped groove being present between the inner wall and the outer wall, and the globe is bonded to the connector using part of the adhesive which is gathered in the groove.
With this construction, an excess of low-viscosity adhesive which is used to form the light diffusion film can be gathered in the groove and put to use for bonding the globe to the connector.
Here, an arch-shaped leaf spring may be formed by cutting part of the inner wall of the connector, wherein the leaf spring presses the neck part which is inserted in the groove, to temporarily tack the connector to the globe until the adhesive gathered in the groove hardens.
With this construction, the globe and the connector can be positioned easily at the time of bonding, with it being possible to avoid displacements.
Here, the inner wall of the connector may have a smaller height than the outer wall of the connector.
With this construction, an excessive amount of adhesive in the groove overflows not from the outer wall but from the inner wall, so that the external appearance of the bulb-type lamp will not be ruined.
Here, a depression and a projection that fit together may be each provided at a facing portion of a different one of the connector and the holder, so that the connector and the holder move in conjunction with a rotation of the globe which is bonded to the connector.
With this construction, when the user installs the bulb-type lamp into a socket, the globe will be kept from becoming unattached from the case and turning freely on its own.
Here, the bulb-type lamp may be an electrodeless discharge lamp in which a core supporter is supported by the stand of the holder, and a coil form on which an induction coil is wound is supported by the core supporter.
The stated object can also be achieved by a manufacturing method for a bulb-type lamp, including: a holding step for holding a holder which has a stand supporting an electric ballast, by a case which has an opening, in a state where the holder is inserted in the case through the opening with the electric ballast being inserted first; a bonding step for bonding a globe which has a constricted neck part at one end, to a connector which has a ring-shaped groove in which the neck part of the groove can be inserted, in a state where the neck part is inserted in the groove; and a fixing step for fixing the connector to which the globe is bonded, to one of the case and the holder by a fitting construction, in the opening of the case.
With this method, the globe is held in place just by engaging the connector, to which the globe is bonded, with the case or the holder. This eliminates the need for the heating process which is conventionally performed after the envelope is formed by the globe and case. Accordingly, the tilting of the globe caused by the expansion of air in the envelope is prevented, with it being possible to hold the globe without a tilt relative to the case. As a result, the external appearance of the bulb-type lamp improves. This reduces the number of defective products, so that increases of manufacturing costs caused by abandoning defective products can be suppressed.
Here, in the bonding step a fixed distance may be maintained between a furthermost end of the connector and a furthermost end of the globe, wherein an adhesive is injected into the groove while keeping the neck part which is inserted in the groove from contact with a bottom of the groove, to bond the globe to the connector.
The globe is usually formed from glass and therefore tends to have variations in size. However, if the globe is bonded to the connector by injecting the adhesive into the groove while maintaining a fixed distance between the furthermost ends of the connector and globe and also keeping the neck part of the globe from contact with the bottom of the groove, the globe and the connector are held together without a tilt. As a result, a bulb-type lamp with a uniform height can be produced.
Here, the bulb-type lamp may be a bulb-type fluorescent lamp in which (a) the globe is a hollow spherical member having an open end at which the neck part is formed, and (b) a light diffusion film is formed on an internal surface of the globe using an adhesive in which a light diffusion material is dispersed, wherein when the adhesive is applied to the internal surface of the globe to form the light diffusion film, an excess of the adhesive drops and is gathered in the groove of the connector, the gathered adhesive being used to bond the globe to the connector in the bonding step.
With this construction, the adhesive used for forming the light diffusion film is also used for bonding the globe to the connector. This contributes to lower manufacturing costs.